Payout net calculations slightly below expected values

[leopoldjoy]

If I call the report subcommand for cycle 103:

./payman report --delegate=tz1Z3KCf8CLGAYfvVWPEr562jDDyWkwNF7sT --cycle=103 --node=https://mainnet.tezrpc.me --fee=0.1 --payout-min=10000

One of the values I receive in the report is the following:

+--------------------------------------+-----------+------------+-----------+------------+
|               ADDRESS                |   SHARE   |   GROSS    |    FEE    |    NET     |
+--------------------------------------+-----------+------------+-----------+------------+
| KT1SZW1BpgPibbiRc9aqtqXeKKh4fe56XyZB |  1.571122 |   2.592351 |  0.259235 |   2.333116 |
...

This suggests that for delegator KT1SZW1BpgPibbiRc9aqtqXeKKh4fe56XyZB the following are the calculated values for cycle 103:

Gross Payout: 2.592351 ꜩ
Net Payout: 2.333116 ꜩ

However, if you call the TzScan API as follows:

http://api6.tzscan.io/v1/rewards_split/tz1Z3KCf8CLGAYfvVWPEr562jDDyWkwNF7sT?cycle=103&p=0

You will get the following values:

{
  "delegate_staking_balance":"210040925181",
  "delegators_nb":29,
  "delegators_balance":[
    [
      {
        "tz":"KT1SZW1BpgPibbiRc9aqtqXeKKh4fe56XyZB"
      },
      "3300000000"
    ],
    ...
  ],
  "blocks_rewards":80000000,
  "endorsements_rewards":85000000,
  "fees":12293,
  "future_blocks_rewards":0,
  "future_endorsements_rewards":0,
  "gain_from_denounciation":0,
  "lost_deposit_from_denounciation":0,
  "lost_rewards_denounciation":0,
  "lost_fees_denounciation":0,
  "revelation_rewards":0,
  "lost_revelation_rewards":0,
  "lost_revelation_fees":0
}

As we can see, this delegator should receive the following percentage of all rewards and fees:

3300000000 / 210040925181 = 0.01571122388 = %1.571122388

We can also see that the total rewards and fees accrued by the baker for this round are as follows:

80000000 + 85000000 + 12293 = 165012293

Finally, we can calculate that the gross payout for this delegator should be as follows:

0.01571122388 * 165012293 = 2592545.07827516

And by removing the bakers fee (10%), we get:

2592545.07827516 * 0.9 = 233329057044764.4

Finally, by switching back to XTZ and rounding to 6 decimal places, we get:

Gross Payout: 2.592545 ꜩ
Net Payout: 2.333291 ꜩ

Thus, we can see that there is a small discrepancy between the payouts that Payman is calculating and the values we manually calculated (0.000194 ꜩ discrepancy for the Gross Payout, or 0.000175 ꜩ of the Net Payout). Additionally, we can see that Baking Bad also shows an expected payout of 2.333291 ꜩ:

This payout discrepancy bug is present in all entries returned by a report.

[DefinitelyNotAGoat]

Thanks for reporting! A couple thoughts, it could be a discrepancy between how tzscan.io's backend rounds to how GoLangs stdlib rounds. I do a lot of string conversions because the Tezos API uses strings instead of integers to display rewards, It's possible there's some data loss in there. What do you think?

[DefinitelyNotAGoat]

This could probably be resolved easier by creating test cases that ping tzscan and then internally calculate, and compare. So I'm going to write those tests first.

[leopoldjoy]

@DefinitelyNotAGoat Yes, I agree that it seems like a rounding issue—probably a discrepancy arising from those conversations. I'll take a look also, happy to help with these tests 👍

[DefinitelyNotAGoat]

This is resolved with the switch to TZKT.